Informed that she would face "a Thai girl" for a place in the last eight, Jelena Jankovic replied: "Tiger? Tiger who? Tiger Woods?" There were no drivers in evidence, but there was clubbing aplenty as the cull of the top women continued with Jankovic, the second seed, battered into submission 6-3, 6-2 by world No60 Tamarine Tanasugarn.

Against an opponent who forced her to cover almost every blade of the Court 18 grass, Jankovic was woefully short of her best. The Serbian world No3 made 19 unforced errors, hit five double faults and created just two break points. Her defeat, which was followed by No4 seed Svetlana Kuznetsova's three-set dismissal at the hands of Poland's Agnieszka Radwanska - and comes hard on the heels of early exits for Ana Ivanovic, the the world No1, and former champion Maria Sharapova - means that, for the first time in history, none of the top four ladies will feature in the last eight at the All England Club.

In mitigation, Jankovic was hampered by a knee problem sustained during Saturday's three-set win over Polish teenager Caroline Wozniacki. Her movement was impeded and her distress palpable as any hope of remaining on course for a maiden grand slam title - and with it, the world No1 ranking - slowly unravelled. She later had harsh words for the scheduling committee, questioning the logic behind the timing and location of the match.

"I was really not happy with the scheduling," said Jankovic. "I asked to play a little bit later on in the day, which would give me a few more hours to recover and do another therapy [session] in the morning. And why is the number two seed playing on Court 18? It's also not normal that Venus plays on number two, and then Chakvetadze and Vaidisova - who are 18 seed and I don't know which seed - are on Court Number One. I think it makes really no sense."

It is easy to feel sympathy for Jankovic, a likeable character whose assault on the majors has been repeatedly undermined by injury this year. A buttock injury hampered her progress in Australia, while the swollen arm she suffered in Paris had her likening herself to Popeye. Yet her apparent ignorance of an opponent with an impressive grass-court pedigree is less easy to forgive.

Tanasugarn, a former junior Wimbledon finalist, has enjoyed some of her best results on the green stuff. She won the Ordina Open in the build-up to Wimbledon, beating recent French Open finalist Dinara Safina, and has reached the fourth round at the All England Club six times, her best record in the majors by a distance.

If Jankovic knew nothing about the Thai veteran before, she does now. Jankovic was a set behind in 36 minutes as Tanasugarn intelligently exploited the angles, pulling the Serb out of court before closing down the net behind some hefty ground strokes.

Having missed a break point at 2-1 down in the second when Tanasugarn capped a beautifully-crafted baseline exchange with a forehand drive volley, Jankovic, helped by a superb topspin backhand lob, retrieved a break at 4-1. But when she opened the next game with a double fault, Tanasugarn required no further invitation, breaking again before serving out to reach her first quarter final.

Tanasugarn will now face defending champion Venus Williams, who came through 6-3, 6-4 against Russia's Alisa Kleybanova. Williams was 5-1 up in the second set before a belated show of defiance from the 18-year-old set up an entertaining finale. The possibility of a repeat of the all-Williams finals of 2002 and 2003 moved closer after Serena joined her sister in the last eight with a straight sets win over America's Bethany Mattek, 6-3, 6-3.

Elsewhere, world No133 Zheng Jie, the third-round conqueror of top seed Ana Ivanovic, continued her extraordinary run with a 6-3, 6-4 win over Agnes Szavay, the Hungarian 15th seed. Zheng, the first wildcard entrant in history to reach the women's quarter-finals, will play No18 seed Nicole Vaidisova, who beat Anna Chakvetadze in straight sets.

The quarter-final line-up was completed by Radwanska's 6-4, 1-6, 7-5 victory over Kuznetsova. The No14 seed recovered from 3-1 down in the final set to win in two hours and four minutes. The 19-year-old will face Serena Williams in the last eight; their only previous encounter, on clay in Berlin earlier this year, resulted in a straight sets win for Williams.